About the series
UFO was the Andersons' first totally live-action TV series. Despite the assumption of many TV station executives, the series was not aimed at children but deliberately sought an older audience; many episodes featured adult themes such as adultery, divorce, and drug use. 
Most of the cast were newcomers to Century 21 although star Ed Bishop had previously worked with the Andersons as a voice actor on Captain Scarlet and The Mysterons. UFO first aired in the UK and Canada in 1970 and in US syndication over the next two years. In all, 26 episodes, including the pilot, were filmed over the course of more than a year, with a five-month production break caused by the ultimate closure of the MGM-British Studios in Borehamwood, where the show was initially made.
An idiosyncrasy of the series is that the term "UFO" is pronounced as a word ("you-foh"), as suggested by the real-world originator of the term Edward J. Ruppelt, and not as the more common "you-eff-oh". This is particularly true of the lead character, Ed Straker. Technically speaking the series title should properly be pronounced "you-foh" as well. However, the "you-foh" pronunciation was not consistently applied and some supporting characters use the now more common form. Lead actors Ed Bishop and Michael Billington died in June 2005, within five days of each other.